Battery charge and discharge system for inhibiting or permitting charging of an auxilary battery

ABSTRACT

The present invention provides a battery charge and discharge system whereby a cost reduction can be achieved due to a reduction in count of components constituting the system, and a battery charge and discharge system which controls the charge of an auxiliary battery installed separately from a main battery, has a slave with the auxiliary battery mounted thereon, which is communicably connected with a master and controls the permission/inhibition of the charging of the auxiliary battery based on the judgments of whether or not the master is in sleep mode.

TECHNICAL FIELD

The present invention relates to a battery charge and discharge systemand, more particularly, to a battery charge and discharge system of anapparatus on which an auxiliary battery is mounted.

BACKGROUND ART

As an apparatus having an auxiliary battery mounted thereon, whichcharges and discharges the auxiliary battery, a vehicle security systemis exemplified.

FIG. 7 is a block diagram schematically showing the principal part of aconventional security system. A master 1A as a security device sidecomprises a microcomputer 1 a to perform various types of control.Connected to input terminals of the microcomputer 1 a are an ignitionswitch 2 to detect whether the position of an ignition key is ON or OFF,a key insert switch 3 to detect whether or not the ignition key isinserted into a key cylinder of an engine, a door courtesy switch 4 todetect whether doors are open or closed, a lock position switch 5 todetect whether the doors are locked or unlocked, and an intrusiondetecting means 6 to detect unfair intrusion into a car.

The microcomputer 1 a of the master 1A and a microcomputer 2 a of aslave 2A are connected through a communication line 9. A siren, forexample, as the slave side has the microcomputer 2 a to perform varioustypes of control. An alarm generating circuit 11 is connected to anoutput terminal of the microcomputer 2 a. The alarm generating circuit11 sounds an alarm based on a detected signal from the intrusiondetecting means 6. An ignition detecting circuit 12 is connected to aninput terminal of the microcomputer 2 a, and an ignition key switch 13is connected through a signal wiring 14 to the ignition detectingcircuit 12. One end of an auxiliary battery 15 is connected to themicrocomputer 2 a in order to inform the charge state, while to theother end thereof, a main battery 7 is connected through a switchcircuit 16 and a feeder line 8. The main battery 7 is connected throughthe feeder line 8 to both the microcomputer 1 a of the master 1A and themicrocomputer 2 a of the slave 2A.

Charging of the auxiliary battery 15 mounted on the siren as the slave2A in the above construction has been conducted as follows.

In the slave 2A, an ON/OFF signal of the ignition key switch 13 iscaptured through the signal wiring 14 by the ignition detecting circuit12, which then outputs the detected signal to the microcomputer 2 a.When the ignition key switch 13 is judged to be ON, the microcomputer 2a judges the engine to be in action and sends a signal for making theswitch circuit 16, comprising a switching element such as a transistor,ON to the switch circuit 16 in order to charge the auxiliary battery 15.When the switch circuit 16 becomes ON, the charge of the auxiliarybattery 15 is carried out by the main battery 7 through the feeder line8.

On the other hand, when the ignition key switch 13 is judged to be OFF,the microcomputer 2 a does not judge the engine to be in action andsends a signal for making the switch circuit 16 OFF to the switchcircuit 16 in order to inhibit the charge of the auxiliary battery 15.When the switch circuit 16 becomes OFF, the charge of the auxiliarybattery 15 by the main battery 7 through the feeder line 8 is inhibited.As described above, the charging of the auxiliary battery 15 has beenperformed based on the ON/OFF state of the ignition key switch 13directly detected by the slave 2A.

In the above-described conventional battery charge and discharge system,the signal wiring 14 for capturing the ON/OFF signal from the ignitionkey switch 13 on the slave side is required. In addition, the slave sideis required to have the detecting circuit 12 for detecting the ON/OFFstate of the ignition key switch 13. Therefore, the count of componentsconstituting the slave is large, resulting in a high cost.

DISCLOSURE OF INVENTION

The present invention was developed in order to solve the above problem,and it is an object of the present invention to provide a battery chargeand discharge system, wherein instead of making a slave directly judgethe permission/inhibition of charging of an auxiliary battery mounted onthe slave, the charging of the auxiliary battery is carried out throughthe use of a communication means between a master and the slave, so thatthe count of components such as a signal wiring and a detecting circuitcan be reduced, leading to a reduction in cost.

In order to achieve the above object, a battery charge and dischargesystem (1) according to the present invention is characterized by abattery charge and discharge system controlling the charge and dischargeof an auxiliary battery installed separately from a main battery,wherein a master and a slave with the auxiliary battery mounted thereonare communicably connected, the system comprising a first judging meansto judge whether or not the master is in sleep mode, a charge inhibitmeans to inhibit the charging of the auxiliary battery of the slave whenthe first judging means judges the master to be in sleep mode, and acharge permit means to permit the charging of the auxiliary battery ofthe slave when the first judging means does not judge the master to bein sleep mode.

Using the above battery charge and discharge system (1), the slave cancontrol the permission/inhibition of the charging of the auxiliarybattery based on the judgment of whether or not the master is in sleepmode. Therefore, a signal wiring and a signal detecting circuitcomponent for detecting signals, conventionally required for directlyjudging the state of an ignition key switch on the slave side, becomeneedless, so that the count of components constituting the system can bedecreased, resulting in a cost reduction.

A battery charge and discharge system (2) according to the presentinvention is characterized by a battery charge and discharge systemcontrolling the charge and discharge of an auxiliary battery installedseparately from a main battery, wherein a master and a slave with theauxiliary battery mounted thereon are communicably connected, the systemcomprising a second judging means to judge whether or not the sleepconditions of the master are satisfied, a charge inhibit means toinhibit the charging of the auxiliary battery of the slave when thesecond judging means judges the sleep conditions of the master to besatisfied, and a charge permit means to permit the charging of theauxiliary battery of the slave when the second judging means does notjudge the sleep conditions of the master to be satisfied.

Using the above battery charge and discharge system (2), the slave cancontrol the permission/inhibition of the charging of the auxiliarybattery based on the judgment of whether or not the sleep conditions ofthe master are satisfied. Therefore, a signal wiring and a signaldetecting circuit component for detecting signals, conventionallyrequired for directly judging the state of an ignition key switch on theslave side, become needless, so that the count of componentsconstituting the system can be decreased, resulting in a cost reduction.Moreover, the charge can be inhibited at an earlier timing before themaster goes into sleep mode, and at the wake-up time of the master, thecharging of the auxiliary battery is not permitted until an operationcondition such as an event occurs. As a result, the power consumption ofthe main battery can be reduced.

A battery charge and discharge system (3) according to the presentinvention is characterized by a battery charge and discharge systemcontrolling the charge and discharge of an auxiliary battery installedseparately from a main battery, wherein a master and multiple nodes areconnected through a communication line, and the master and a slave withthe auxiliary battery mounted thereon are communicably connected, thesystem comprising a third judging means to judge whether or not at leastone of the nodes is in sleep mode, a charge inhibit means to inhibit thecharging of the auxiliary battery of the slave when the third judgingmeans judges at least one of the nodes except for the master to be insleep mode, and a charge permit means to permit the charging of theauxiliary battery of the slave when the third judging means judges noneof the nodes except for the master to be in sleep mode.

Using the above battery charge and discharge system (3), the slavereceives the judgment of whether or not the nodes connected through thecommunication line with the master are in sleep mode through thecommunication line and controls the permission/inhibition of thecharging of the auxiliary battery. Therefore, a signal wiring and asignal detecting circuit component for detecting signals, conventionallyrequired for directly judging the state of an ignition key switch on theslave side, become needless, so that the count of componentsconstituting the system can be reduced, resulting in a cost reduction.Moreover, by receiving at an early stage a signal indicating that thecommunication system including the multiple nodes is shifting to sleepmode while the master itself is in action, the charging of the auxiliarybattery can be inhibited at an earlier timing. And at the wake-up timeof the master, the charging of the auxiliary battery is not permitteduntil all of the nodes go into action. As a result, the powerconsumption of the main battery can be reduced.

A battery charge and discharge system (4) according to the presentinvention is characterized by the auxiliary battery, which is used as adriving power when the electric power supply from the main battery iscut off in any of the battery charge and discharge systems (1)-(3)

Using the above battery charge and discharge system (4), even if theelectric power supply is cut off by causing the main battery to beremoved, or the feeder line from the main battery to be cut, the drivingpower can be supplied from the auxiliary battery, resulting inmaintaining the slave in action.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram schematically showing the principal part of abattery charge and discharge system according to embodiments (1)-(3) ofthe present invention;

FIG. 2 is a flow chart showing the operation of a microcomputer in abattery charge and discharge system according to the embodiment (1);

FIG. 3 is a flow chart showing the operation of a microcomputer in abattery charge and discharge system according to the embodiment (2);

FIG. 4 is a block diagram schematically showing an example of theoverall construction of a battery charge and discharge system accordingto the embodiment (3);

FIG. 5 is a flow chart showing the operation of a microcomputer in thebattery charge and discharge system according to the embodiment (3);

FIG. 6 is a timing chart showing the permission/inhibition control ofcharging of an auxiliary battery in each of the battery charge anddischarge systems according to the embodiments (1)-(3); and

FIG. 7 is a block diagram schematically showing the principal part of aconventional battery charge and discharge system.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiments of the battery charge and discharge systemaccording to the present invention are described below by reference tothe Figures of the drawings.

FIG. 1 is a block diagram schematically showing the principal part of abattery charge and discharge system according to an embodiment (1).Here, the same marks are affixed to the components similar to those ofthe conventional battery charge and discharge system shown in FIG. 7,the description of which will not be repeated.

A microcomputer 10 a of a master 10A and a microcomputer 20 a of a slave20A are connected through a communication line 9 a. The master 10Acomprises the microcomputer 10 a, and to input terminals of themicrocomputer 10 a, each of an ignition switch 2, a key insert switch 3,a door courtesy switch 4, a lock position switch 5, and an intrusiondetecting means 6 are connected so that each detected signal is inputthereto. The slave 20A as a siren comprises the microcomputer 20 a, anauxiliary battery 15, a switch circuit 16, and an alarm generatingcircuit 11. And the electric power from a main battery 7 is supplied tothe microcomputer 10 a of the master 10A, the microcomputer 20 a of theslave 20A, and the auxiliary battery 15 through a feeder line 8.

The battery charge and discharge system according to the embodiment (1)is operated as follows.

When the battery charge and discharge system shifts to sleep mode, it isdetected through the ignition switch 2 that the ignition key switch wasmade OFF; by a detected signal from the key insert switch 3, it isdetected that the ignition key was removed from the key cylinder; by adetected signal from the door courtesy switch 4, it is detected that allof the doors are closed; and by a detected signal from the lock positionswitch 5, it is detected that the door lock mechanisms are in the lockedstate, leading to the satisfaction of the conditions for shifting toalert mode. Then, the master 10A shifts to the alert mode for monitoringand guarding against unfair intrusion into the car. When the master 10Agoes into the alert mode, the microcomputer 10 a thereof shifts to thesleep mode (low electric current consumption mode) in order to lower thepower consumption to a minimum.

In the slave 20A, when the microcomputer 20 a receives a signalindicating that the master 10A is in sleep mode through thecommunication line 9 a, a control signal for inhibiting the charge ofthe auxiliary battery 15 is sent from the microcomputer 20 a to theswitch circuit 16 in order to cut off the feeder line from the mainbattery 7 to the auxiliary battery 15, so that the charge of theauxiliary battery 15 is inhibited. Then, the microcomputer 20 a on theslave 20A side also shifts to sleep mode.

On the other hand, in order that the master 10A in the sleep mode mayshift to wake-up mode (normal electric current consumption mode), it isconditioned that a door should be unlocked with a key in the normal way,and that an ON signal of the ignition switch 2 should be input to themicrocomputer 10 a. When these conditions are met, the master 10A shiftsto the wake-up mode from the sleep mode. When the microcomputer 20 a ofthe slave 20A receives a signal indicating that the master 10A is in thewake-up mode through the communication line 9 a, the microcomputer 20 athereof also shifts to wake-up mode and sends a signal for permittingthe charge of the auxiliary battery 15 to the switch circuit 16, whichmakes the switch circuit 16 ON so as to enable the charge of theauxiliary battery 15 by the main battery 7.

The control operation of the charging of the auxiliary battery 15 by themicrocomputer 20 a in that battery charge and discharge system isdescribed by reference to a flow chart shown in FIG. 2.

In Step 1, in order to check the operating mode of the master 10A, themicrocomputer 20 a captures a signal from the microcomputer 10 a throughthe communication line 9 a. In Step 2, it judges whether or not themaster 10A is in sleep mode. When it judges the master 10A to be insleep mode, it goes to Step 3, wherein the inhibition of theabove-described charge of the auxiliary battery 15 is conducted and thenfinished. On the other hand, when it does not judge the master 10A to bein sleep mode in Step 2, it goes to Step 4, wherein the permission ofthe above-described charge of the auxiliary battery 15 is conducted andthen finished.

The timing chart of the permission/inhibition of the charging of theauxiliary battery 15 in this case is shown in FIG. 6(a). T₁₁ is theinstant when the master 10A was judged to be in sleep mode, since whenthe charge of the auxiliary battery 15 has been inhibited. And T₁₂ isthe instant when the master 10A was judged to have shifted from thesleep mode to wake-up mode, since when the charge of the auxiliarybattery 15 has been permitted.

Using the battery charge and discharge system according to theembodiment (1), the slave 20A captures a signal indicating the judgmentof whether or not the master 10A is in sleep mode through thecommunication line 9 a, whereby it can control the permission/inhibitionof the charging of the auxiliary battery 15. Therefore, a wiring forcapturing signals (a signal wiring 14 shown in FIG. 7) and a signaldetecting circuit component for detecting signals (an ignition detectingcircuit 12 shown in FIG. 7), conventionally required for directlyjudging the state of the ignition key switch on the slave 20A side,become needless. As a result, the count of components constituting thesystem can be decreased, leading to a cost reduction.

A battery charge and discharge system according to an embodiment (2) isdescribed below.

The hardware construction of the battery charge and discharge systemaccording to the embodiment (2) is the same as that of the batterycharge and discharge system shown in FIG. 1, which is not describedhere.

The different point of the battery charge and discharge system accordingto the embodiment (2) from the battery charge and discharge systemaccording to the embodiment (1) is that the charge of an auxiliarybattery 15 is inhibited at an earlier stage than in the battery chargeand discharge system according to the embodiment (1). When a mastershifts to sleep mode, usually the master shifts to the sleep modeseveral seconds after the conditions for sleep were met. But in the caseof the embodiment (2), at the stage where the conditions for sleep of amaster 10B were met, that signal is captured by a microcomputer 20 b ofa slave 20B through a communication line 9 a, and the charge of theauxiliary battery 15 is inhibited.

The control operation of the charging of the auxiliary battery 15 by themicrocomputer 20 b in the battery charge and discharge system accordingto the embodiment (2) is described by reference to a flow chart shown inFIG. 3.

In Step 11, in order to check the operating mode of the master 10B, themicrocomputer 20 b captures a signal from the microcomputer 10 b throughthe communication line 9 a. In Step 12, it judges whether or not thesleep conditions of the master 10B are satisfied. It may be set so thatit can judge whether or not the sleep conditions are satisfied from adetected signal from a key insert switch 3 and the like as necessary.When it judges the sleep conditions to be satisfied in Step 12, it goesto Step 13, wherein the inhibition of the charge of the auxiliarybattery 15 is conducted and then finished. On the other hand, when itdoes not judge the sleep conditions to be satisfied in Step 12, it goesto Step 14, wherein the permission of the charge of the auxiliarybattery 15 is conducted and then finished.

The timing chart of the permission/inhibition of the charging of theauxiliary battery 15 in this case is shown in FIG. 6(b). T₂₁ is theinstant when the sleep conditions of the master 10B were judged to besatisfied, since when the charge of the auxiliary battery 15 has beeninhibited. There is a time lag of about several seconds between theinstant T₂₁ and the instant T₁₁ when the master 10A went into sleep modein FIG. 6(a). And T₂₂ is the instant when the master 10B shifted fromthe sleep mode to wake-up mode and an operation condition occurred tothe microcomputer 10 b, which made it impossible for the master 10B togo into sleep mode, since when the charge of the auxiliary battery 15has been permitted.

Using the battery charge and discharge system according to theembodiment (2), the slave 20B captures the judgment of whether or notthe sleep conditions of the master 10B are satisfied through thecommunication line 9 a, and controls the permission/inhibition of thecharging of the auxiliary battery 15 based on the judgment. Therefore, awiring for capturing signals (a signal wiring 14 shown in FIG. 7) and asignal detecting circuit component for detecting signals (an ignitiondetecting circuit 12 shown in FIG. 7), conventionally required fordirectly judging the state of an ignition key switch on the slave side,become needless. As a result, the count of components constituting thesystem can be decreased, leading to a cost reduction. Moreover, thecharging can be inhibited at an earlier timing before the master goesinto sleep mode, while at the wake-up time of the master 10B, the powerconsumption of the main battery 7 can be further reduced, since thecharging of the auxiliary battery 15 is not permitted until an operationcondition such as an event occurs to the microcomputer 10 b.

A battery charge and discharge system according to an embodiment (3) isdescribed here.

FIG. 4 is a block diagram showing an example of the overall constructionof a battery charge and discharge system according to the embodiment(3). The hardware construction of a master 10C and a slave 20C is thesame as that of the master 10A and the slave 20A according to theembodiment (1) shown in FIG. 1 except for an external communicationmeans 17 additionally arranged to input and output signals to and from acommunication line 21 for communicating with multiple nodes, which isnot described in detail here.

In the battery charge and discharge system according to the embodiment(3), nodes 30-60 and the master 10C, mounted on a vehicle, are connectedin the form of a ring through the communication line 21, resulting inthe construction of a vehicle LAN which enables them to shareinformation with one another by communication. As an access method forcontrolling the data transmission by the ring-type communication line21, a token passing method is adopted. Here, the access method forcommunication is not limited to this embodiment, and depending on theconnecting method of the communication line with each node (of a bustype, a ring type, a star type and the like), an optimum access methodmay be selected and adopted as necessary.

Each node 30, 40, 50 or 60 is not specifically limited, and each nodehas only to be mounted on a vehicle, control the system using amicrocomputer, and have a transmitting-receiving function forcommunication. For example, as the nodes 30, 40, 50 and 60, an ECU forengine control, an ECU for body control, an ECU for seat control, and anECU for meter control can be adopted, respectively.

The control operation of the charging of the auxiliary battery 15conducted by the microcomputer 20 c (FIG. 1) in the battery charge anddischarge system according to the embodiment (3) is described byreference to a flow chart shown in FIG. 5.

In Step 21, in order to check the operating mode of each node 30, 40, 50or 60, the microcomputer 20 c captures signals from the microcomputer 10c through the communication line 9 a. The microcomputer 20 c demands themicrocomputer 10 c of the master 10C through the communication line 9 ato transmit the signals of whether or not each node 30, 40, 50 or 60 isin sleep mode, sent from each of them to the microcomputer 10 c bycommunication through the communication line 21. Then, it goes to Step22, wherein it judges whether or not at least one of the nodes 30-60 isin sleep mode. When at least one of the nodes 30-60 is judged to be insleep mode in Step 22, it goes to Step 23, wherein the inhibition of thecharging of the auxiliary battery 15 is conducted and then finished. Onthe other hand, when none of the nodes 30-60 are judged to be in sleepmode in Step 22, it goes to Step 24, wherein the permission of thecharging of the auxiliary battery 15 is conducted and then finished.

The timing chart of the permission/inhibition of the charging of theauxiliary battery 15 in this case is shown in FIG. 6(c). T₃₁ indicatesthe instant when at least one of the multiple nodes 30-60 was judged tobe in sleep mode, since when the charge of the auxiliary battery 15 hasbeen inhibited. Compared with FIG. 6(a) wherein the instant is when themaster 10 goes into sleep mode and FIG. 6(b) wherein the instant is whenthe sleep conditions of the master 10B are satisfied, the charge of theauxiliary battery 15 is inhibited at an earlier timing. T₃₂ indicatesthe instant when all of the nodes 30-60 shifted from the sleep mode towake-up mode, and an operation condition occurred, since when the chargeof the auxiliary battery 15 has been permitted. Compared with FIG. 6(a)wherein the instant is when the master 10A goes into wake-up mode andFIG. 6(b) wherein the instant is when an operation condition occurred tothe master 10B, the charge of the auxiliary battery 15 is permitted at alater timing.

Using the battery charge and discharge system according to theembodiment (3), the slave 20C receives the judgment of whether or noteach node 30, 40, 50 or 60 connected through the communication line 21with the master 10C is in sleep mode from the microcomputer 10 c throughthe communication line 9 a, and controls the permission/inhibition ofthe charging of the auxiliary battery 15. Therefore, a wiring forcapturing signals (a signal wiring 14 shown in FIG. 7) and a signaldetecting circuit component for detecting signals (an ignition detectingcircuit 12 shown in FIG. 7), conventionally required for directlyjudging the state of an ignition key switch on the slave 20C side,become needless. As a result, the count of components constituting thesystem can be decreased, leading to a cost reduction. Moreover, byreceiving at an early stage a signal indicating that the communicationsystem including the multiple nodes 30-60 is shifting to sleep modewhile the master 10C itself is in action, the charge of the auxiliarybattery 15 can be inhibited at an earlier timing. And at the wake-uptime of the master 10C, the charge of the auxiliary battery 15 is notpermitted until all of the nodes 30-60 are actuated, so that the powerconsumption of the main battery 7 can be further reduced.

Here, as a master 10A, 10B or 10C, and a slave 20A, 20B or 20C, thoserelated to a security system are exemplified in the above embodiments,but the present invention is not limited to the above embodiments. Thepresent invention is applicable and advantageous to any system wherein amaster and a slave with an auxiliary battery mounted thereon arecommunicably connected. For example, it can be applied to an emergencycall system or the like.

INDUSTRIAL APPLICABILITY

A battery charge and discharge system according to the present inventionis applicable to any system wherein a master and a slave with anauxiliary battery mounted thereon are communicably connected, and as asystem with an auxiliary battery mounted thereon, which charges anddischarges the auxiliary battery, a vehicle security system, anemergency call system, and the like are exemplified.

What is claimed is:
 1. A battery charge and discharge system whichcontrols the charge and discharge of an auxiliary battery installedseparately from a main battery, wherein a master and a slave arecommunicably connected, and the auxiliary battery is mounted on theslave, the system comprising: a judging means for judging whether or notthe master is in sleep mode; a charge inhibit means for inhibiting thecharging of the auxiliary battery of the slave when the master is judgedto be in sleep mode by the judging means; and a charge permit means forpermitting the charging of the auxiliary battery of the slave when themaster is not judged to be in sleep mode by the judging means.
 2. Abattery charge and discharge system which controls the charge anddischarge of an auxiliary battery installed separately from a mainbattery, wherein a master and a slave are communicably connected, andthe auxiliary battery is mounted on the slave, the system comprising: ajudging means for judging whether or not sleep conditions of the masterare satisfied; a charge inhibit means for inhibiting the charging of theauxiliary battery of the slave when the sleep conditions of the masterare judged to be satisfied by the judging means; and a charge permitmeans for permitting the charging of the auxiliary battery of the slavewhen the sleep conditions of the master are not judged to be satisfiedby the judging means.
 3. A battery charge and discharge system whichcontrols the charge and discharge of an auxiliary battery installedseparately from a main battery, wherein a master and multiple nodes areconnected through a communication line; and the master and a slave arecommunicably connected, and the auxiliary battery is mounted on theslave, the system comprising: a judging means for judging whether or notat least one of the nodes is in sleep mode; a charge inhibit means forinhibiting the charging of the auxiliary battery of the slave when atleast one of the nodes except for the master is judged to be in sleepmode by the judging means; and a charge permit means for permitting thecharging of the auxiliary battery of the slave when none of the nodesexcept for the master are judged to be in sleep mode by the judgingmeans.
 4. A battery charge and discharge system according to claim 1,wherein the auxiliary battery is used as a driving power when theelectric power supply from the main battery is cut off.
 5. A batterycharge and discharge system according to claim 2, wherein the auxiliarybattery is used as a driving power when the electric power supply fromthe main battery is cut off.
 6. A battery charge and discharge systemaccording to claim 3, wherein the auxiliary battery is used as a drivingpower when the electric power supply from the main battery is cut off.7. A battery charge and discharge system for use with a main battery,said system comprising: a master unit having a sleep mode; and a slaveunit operable to communicate with said master unit, said slave unitcomprising: an auxiliary battery; a computer operable to judge whetheror not said master unit is in the sleep mode and to output an indicatingsignal indicative of whether or not said master unit is in the sleepmode; a switch circuit operable to: receive the indicating signal fromsaid computer; inhibit charging of said auxiliary battery by the mainbattery when the indicating signal indicates that the master unit is inthe sleep mode; and permit charging of said auxiliary battery by themain battery when the indicating signal indicates that said master unitis not in the sleep mode.
 8. A battery charge and discharge systemaccording to claim 7, wherein said auxiliary battery provides drivingpower when electric power from the main battery is cut off.
 9. A batterycharge and discharge system for use with a main battery, said systemcomprising: a master unit having a sleep mode into which said masterunit shifts after sleep conditions are satisfied; and a slave unitoperable to communicate with said master unit, said slave unitcomprising: an auxiliary battery; a computer operable to judge whetheror not the sleep conditions of said master unit are satisfied and tooutput an indicating signal indicative of whether or not the sleepconditions of said master unit are satisfied; a switch circuit operableto: receive the indicating signal from said computer; inhibit chargingof said auxiliary battery by the main battery when the indicating signalindicates that the sleep conditions of said master unit are satisfied;and permit charging of said auxiliary battery by the main battery whenthe indicating signal indicates that the sleep conditions of said masterunit are not satisfied.
 10. A battery charge and discharge systemaccording to claim 9, wherein said auxiliary battery provides drivingpower when electric power from the main battery is cut off.
 11. Abattery charge and discharge system accord to claim 9, wherein saidmaster unit shifts into the sleep mode a time period after the sleepconditions are satisfied.
 12. A battery charge and discharge system foruse with a main battery, said system comprising: a communication line;plural nodes; a master unit having a sleep mode, wherein said masterunit and said nodes are connected via said communication line; and aslave unit operable to communicate with said master unit, said slaveunit comprising: an auxiliary battery; a computer operable to judgewhether or not at least one of said nodes is in the sleep mode and tooutput an indicating signal indicative of whether or not at least one ofsaid nodes is in the sleep mode; a switch circuit operable to: receivethe indicating signal from said computer; inhibit charging of saidauxiliary battery by the main battery when the indicating signalindicates that at least one of said nodes is in the sleep mode; andpermit charging of said auxiliary battery by the main battery when theindicating signal indicates that none of said nodes is in the sleepmode.
 13. A battery charge and discharge system according to claim 12,wherein said auxiliary battery provides driving power when electricpower from the main battery is cut off.